Loop setting means for a motion picture projector

ABSTRACT

Automatic loop setting and restoring means to restore the loop in the motion picture film on either side of the film gate. If the loop is lost and the film is pulled tight, a lever is triggered which in turn triggers a gear drive mechanism which rotates the lever to restore the loop.

United States Patent H91" Kongelka lMarch 13, 1973 [54] LOOP SETTINGMEANS FOR A MOTION PICTURE PROJECTOR [76] Inventor: Robert M. Kongelka,315 Allison Ave., Houston, Pa. 15342 22 Filed: June7, 1971 21 Appl.No.:150,507

[52] U.S. CI. ..226/36, 226/44, 226/114,

51 im. Cl. ..B65h 23/16 [58 Field of Search "226/44, 114, 36; 352/159[56] References Cited UNITED STATES PATENTS Cunningham ..226/36 Fox..352/l59 Primary Examiner-Richard A. Schacher Att0rneyJames P. Malone57 ABSTRACT Automatic loop setting and restoring means to restore theloop in the motion picture film on either side of the film gate. If theloop is lost and the film is pulled tight, a lever is triggered which inturn triggers a gear drive mechanism which rotates the lever to restorethe loop.

3 Claims, 3 Drawing Figures RoJzcron pal PATENTEUNARISIHH 3,7 0,3 2

PROJECTOR PROJECTOR FIG 2 2o" INVENTOR. ROBERT M. KONGELKA LOOP SETTINGMEANS FOR A MOTION PICTURE PROJECTOR This invention relates to automaticloop forming means for motion picture projectors and, more particularly,to means to restore a loop in the film after it has been lost.

Motion picture projectors require loops on either side of the film gateto accommodate the intermittent film motion occurring at the film gate.If the loops are lost for any reason and the film is pulled taut, it isliable to be damaged.

The present invention provides a simple adapter, generally comprising alever assembly upon which is mounted a roller. The roller assembly isadapted to be triggerd by the loss of loop. This is accomplished byallowing the lost loop to lift the roller supporting lever apred-determined distance engaging a driving means. With the drivingpower engaged, the roller and lever reverse their direction of traveland pull the correct amount of film thru thegate resetting the loop.

Accordingly, the principal object of the invention is to provide new andimproved loop forming and setting means for motion picture projectors.

Another object of the invention is to provide new and improved looprestoring means to restore a loop after the loop has been lost becauseof,

heavy splices,

worn sprocket holes,

missing holes,

heat damage, or

other discontinuities.

Another object of the invention is to provide in a motion. picture filmprojector of the type having a'frame, a film gate, an output filmsprocket, a toothed belt connected to drive said sprocket, said filmnormally having a loop at the output of said film gate, new and improvedmeans to restore a lost loop in said film at the output of said filmgate, comprising a lever pivotally mounted on said projector, a rollermounted on the end of said lever, said lever being normally in positioninside said loop and out of contact with said film, means to rotate saidlever a predetermined amount to form a loop in said film, said leverbeing connected to trigger said rotation means when said loop is lostand said film comes in contact with said roller.

These and other objects of the invention will be apparent from thefollowing specification and drawings, of which:

FIG. 1 is aside view of a typical projector.

FIG. 2 is a detail view illustrating the drive mechanism for the loopforming lever.

FIG. 3 is a perspective view of a modification of the invention.

The FIG. 1. depicts a standard film path with one addition. The additionis pivoted arm 14 carrying a-small roller-15. In FIG. 1 the solid lineindicates the normal film F path while the dashed section indicates alost loop and'alternate dash and dot line indicates where film must bepulled to restore the loop. The roller is normally held above the film,out of contact when film is being handled properly. If film loop islost" it no longer clears the small roller 15 and the roller is lifted,triggering a mechanism to be described, which pulls sufficient filmthrough the aperture to restore the loop. This is accomplished bypulling film to a lower path in FIG. 1 with the added roller 15. Notethat the motion of the roller is an arc, not a full circle, giving acompact motion suitable for most projection equipment. This motionsupplies sufficient stroke" yet avoids interfering with shutter-aperturehousing and automatic threader supports.

Preferably only roller 15 is visible. All other parts are internal.Roller 15 operates thru a slot in the main frame.

To minimize changes required to install the system into an existingprojector, a timing belt, FIG. 2, having teeth on both sides of itspitch line is substituted for the existing sprocket drive timing belt.The back of the substitute belt supplies the power for the mechanismthat drives the arm 14 and roller 15 added to the machine.

Mounted on a center close enough to the belt so as to be in mesh withthe outside teeth on the dual tooth" belt is a timing pulleyalternatively we could use smooth pulley with a flat and flat belt withsufficient tension and flanges. The size of this pulley has a directeffect on restorer action. A 24 tooth pulley gives sufficient drivingtorque and a slow, gentle action with the geometry used, for instance,in the Viewlex Super 1600. The pulley or gear being described has twoflat areas of importance: (1) a fiat region 24 on its circumference thathas teeth removed allowing a position where the belt cannot drive thepulley. (2) a flat on a cam 27 surface attached to the pulley thatassures the pulley always stops out of belt engagement. The cam surfaceand hence the pulley is positioned by a light spring riding on it. i

Referring, more specifically, to FIG. 1, there is shown a typical motionpicture projector 1 having a lens housing 2 and a film gate 3. The filmF is driven by the input sprocket 4 and the output sprocket 5. Thesprockets are driven by a toothed belt 6. Loops 7 and 8 are necessary toprovide for the intermittent motion of the film within the film gate.When the film exits from the gate at the bottom of the projector, itpasses around guide rollers 10, 12, to the output sprocket 5. Roller 11is typically a stabilizing roller attached to the fly wheel. Referringto the lower loop 8, if it is lost due to some film discontinuity or forsome other reason, then the film will assume the position shown by thedotted lines 13. The film in this position is already damaged to someextent for it to have difficulty going thru machine smoothly. At thispoint film is in continuous motion causing a smear of moving frames onthe screen. The auto setter eliminates stopping the presentation toreset film. In order to restore the loop, a lever 14 is provided uponwhich is mounted a roller 15. A drive mechanism is provided, as shown inFIG. 2 for driving the lever. In order to form a proper loop, as shownin the full line, it is necessary to make a loop as shown in thedash-dot lines.

Referring to FIGS. 1 and 2, lever 14 is pivotally mounted at 14' on thelens casing 2. The roller 15 normally fits inside the loop 8 and out ofcontact with the film. If the lower film path is shortened as shown bythe dotted lines, then the film raises the lever 14 and roller 15 to thepoint 20. When this happens, portion 21 of the lever bears against theraised arcuate portion 22 of the gear 23 which has frictional engagementwith lever 14. Gear 23 is a mutilated gear having a flat side 24 and aplurality of teeth which are adapted to engage the teeth on the drivebelt 6. When the lever 14 and roller are triggered to the position bythe film when the loop is lost, then the portion 21 of the lever pressesdown on the raised projection 22 and rotates the gear 23counter-clockwise sufficiently so that the gear teeth 25 engage theteeth on the belt 6. The belt 6 will then rotate the gear 23counterclockwise in FIG. 2 until the teeth become disengaged fromthebelt when the flat portion 24 rotates intothe position shown in FIG.2. This position is indexed by the flat spring 26 bearing on the flatportion of the cam 27, which is mounted on the gear 23. Thiscounterclockwise motion of gear or pulley 23 is transmitted by theraised arcuate portion 22 of lever 14 rotating it and moving roller toposition 30, thereby restoring the loop. After the gear teeth becomedisengaged from the belt, then the weight 28 on the end of the lever 14causes the lever to rotate clockwise in FIG. 2 and raises the roller 20out of contact with the film F to the normal running position shown inFIG. 2.

FIG. 2 is probably a more simple arrangement.

FIG. 1 gives the additional feature of roller 15 being out of the waywhen threading manually.

FIG. 3 shows a perspective view of a modified lever.

To this point the lever in FIG. 2 has been considered rigid. Inpractice,it preferably has spring compliance. This accomplishes twoimportant functions; (I) eliminates need for retraction of claw teeth,since spring 32 winds while film is intermittently held-by the clawteeth. (2) eliminates a mechanical interlock with a threader not shown.This protects both the threader and operator should the roller be setoff with threader in position, for instance, if a small child wouldstart it with a finger. Notice also that this is a good place fortolerance take-up. Either the slot in the main frame or a suitable stopon gate bottom can limit roller full down travel while a surplus can bebuilt-in from cam on timing pulley with excess travel being stored inspring.

In FIG. 3, the lever modification comprises two separate pieces 30, 31,which are connected together by means of the spring 32. When assembled,pin 33 on lever is loaded against bottom of slot 34 in piece 31 byspring 32.

OPERATION A. When loop is lost film lifts roller; this causes other endof roller lever to nudge timing pulley into engagement (R1 gives largeangular displacement to mutilated gear or pulley from a small input). I

B. Pulley engages belt and turns once. The radius R2 gives leversufficient stroke to set loop.

The lever in FIG. 2 is weighted on its left side to keep the roller upin position. A spring could be used. The arcuate projection on pulleyside, (shaded curved area), and the lever end is shaped such that adwell and gradual return of film roller result. FIG. 2 shows aconstruction with all parts preferably hidden internally. This design isadaptable to a situation where the right side of the lever in FIG. 2could be attached to the bottom of lens gate utilizing a quick-connectlink (as in FIG. 1). This would facilitate manual threading since rollerwould now swing out of way with lens gate, rather than have a semi-fixedroller operating through a slot in the main-frame.

The arcuate projection 22 is preferably not a true arc, but has tworadii RI and R2 connected by a smooth curve that when operated againstlever shape allows roller to dwell at bottom of stroke. This givessufficient time for roller to complete stroke in event of springwind-up.

I claim:

1. In a motion picture film projector of the type having a frame, a filmgate, an output film sprocket, a toothed belt connected to drive saidsprocket, said film normally having a loop at the output of said filmgate,

means to restore a lost loop in said film at the output of said filmgate, com prising:

a lever pivotally mounted on said projector,

a roller mounted on the end of said lever, said lever being normally inposition inside said loop and out of contact with said film,

means to rotate said lever a predetermined amount to form a loop in saidfilm,

said lever being connected to trigger said rotation means when said loopis lost and said film comes in contact with said roller,

wherein said means to rotate comprises a mutilated gear having a flatportion, an arcuate projection mounted on one side of said gear,

said gear being adapted to engage said sprocket drive belt when saidrotation means is triggered, said lever being adapted to trigger saidgear when said lever is triggered by a lost loop whereby said gear isrotated a predetermined amount in an arc shaped motion by said drivebelt and said arcuate projection engages said lever and moves said levera predetermined amount to form a loop of predetermined size in saidfilm.

2. Apparatus as in claim 1 having a detent to position said gear.

3. Apparatus as in claim 1 having swing away roller means.

1. In a motion picture film projector of the type having a frame, a filmgate, an output film sprocket, a toothed belt connected to drive saidsprocket, said film normally having a loop at the output of said filmgate, means to restore a lost loop in said film at the output of saidfilm gate, comprising: a lever pivotally mounted on said projector, aroller mounted on the end of said lever, said lever being normally inposition inside said loop and out of contact with said film, means torotate said lever a predetermined amount to form a loop in said film,said lever being connected to trigger said rotation means when said loopis lost and said film comes in contact with said roller, wherein saidmeans to rotate comprises a mutilated gear having a flat portion, anarcuate projection mounted on one side of said gear, said gear beingadapted to engage said sprocket drive belt when said rotation means istriggered, said lever being adapted to trigger said gear when said leveris triggered by a lost loop whereby said gear is roTated a predeterminedamount in an arc shaped motion by said drive belt and said arcuateprojection engages said lever and moves said lever a predeterminedamount to form a loop of predetermined size in said film.
 1. In a motionpicture film projector of the type having a frame, a film gate, anoutput film sprocket, a toothed belt connected to drive said sprocket,said film normally having a loop at the output of said film gate, meansto restore a lost loop in said film at the output of said film gate,comprising: a lever pivotally mounted on said projector, a rollermounted on the end of said lever, said lever being normally in positioninside said loop and out of contact with said film, means to rotate saidlever a predetermined amount to form a loop in said film, said leverbeing connected to trigger said rotation means when said loop is lostand said film comes in contact with said roller, wherein said means torotate comprises a mutilated gear having a flat portion, an arcuateprojection mounted on one side of said gear, said gear being adapted toengage said sprocket drive belt when said rotation means is triggered,said lever being adapted to trigger said gear when said lever istriggered by a lost loop whereby said gear is roTated a predeterminedamount in an arc shaped motion by said drive belt and said arcuateprojection engages said lever and moves said lever a predeterminedamount to form a loop of predetermined size in said film.
 2. Apparatusas in claim 1 having a detent to position said gear.